Polycrystalline silicon epitaxial growth method

Abstract

The invention provides a simpler polycrystalline silicon epitaxial growth method. The method comprises the following steps of: placing a substrate of which the surface is made of a monocrystalline silicon material in an epitaxial cavity; epitaxial gas is introduced into the surface of the substrate, the polycrystalline silicon layer directly grows, the epitaxial gas is trichlorosilane, and the growth temperature ranges from 850 DEG C to 950 DEG C. According to the technical scheme, transition structures such as a seed layer or a seed crystal layer are not grown, and the polycrystalline silicon layer is directly grown. Research finds that the polycrystalline silicon layer can be directly grown as long as trichlorosilane is adopted as a reaction source gas and the growth temperature is ensured to be within the range of 850-950 DEG C.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a polysilicon epitaxial growth method. Background Art

[0002] Epitaxial growth of polysilicon is a common process in the semiconductor field. A typical method in the prior art is to first deposit polysilicon on the surface of a silicon wafer as an epitaxial seed layer, and then epitaxially grow polysilicon on the seed layer to form an epitaxial layer. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a simpler method for epitaxial growth of polysilicon.

[0004] In order to solve the above problems, the present invention provides a polysilicon epitaxial growth method, comprising the following steps: placing a substrate with a surface of single crystal silicon material in an epitaxial cavity; introducing epitaxial gas into the surface of the substrate to directly grow a polysilicon layer, the epitaxial gas is trichlorosilane, and the growth temperature is in the range of 850-950°C.

[0005] Optionally, the substrate is kept at 800-900° C. in an epitaxial furnace, and H2 or N2 is introduced at a flow rate of 40-80 L / min, and the heat preservation time is 40-100 seconds.

[0006] Optionally, the flow rate of the directly grown polysilicon layer is 2-5 L / min.

[0007] The above technical solution does not grow transition structures such as seed layers or seed crystal layers, but directly grows a polysilicon layer. Studies have found that as long as trichlorosilane is used as a reaction source gas and the temperature growth temperature is kept within the range of 850-950°C, a polysilicon layer can be directly grown. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Attached Figure 1 Shown is a schematic diagram of the implementation steps of a specific embodiment of the present invention.

[0009] Attached Figure 2 The following is shown: Figure 1 A scanning electron microscope photograph of a product obtained by one embodiment of the process shown.

[0010] Attached Figure 3 Is the use of attached Figure 1 A photograph of the surface morphology of a product obtained by an embodiment of the process shown.

[0011] Attached Figure 4 Is the use of attached Figure 1 An AFM surface photograph of a product obtained by an embodiment of the process shown. DETAILED DESCRIPTION

[0012] The specific implementation of the polysilicon epitaxial growth method provided by the present invention is described in detail below with reference to the accompanying drawings.

[0013] Attached Figure 1 The figure is a schematic diagram of the implementation steps of this specific embodiment, including: step S10, placing a single crystal silicon substrate in an epitaxial chamber; and step S11, introducing epitaxial gas into the surface of the single crystal silicon substrate to directly grow a polycrystalline silicon layer at a growth temperature in the range of 850-950°C.

[0014] Step S10, placing a single crystal silicon substrate in the epitaxial cavity. In this specific embodiment, the substrate is a single crystal silicon substrate. In other specific embodiments, the substrate can be any substrate with a single crystal silicon material on the surface, including but not limited to a single crystal silicon substrate, a silicon substrate on an insulator, and a substrate in which a single crystal silicon layer is formed on the surface of any semiconductor substrate by bonding-stripping and other processes. In this step, in order to smoothly implement the subsequent process, it is necessary to keep the single crystal silicon substrate in the epitaxial furnace at 800-900°C, introduce H2 or N2, with a flow rate range of 40-80 liters / minute, and keep warm for 40-100 seconds. The above process parameters can be adjusted according to actual conditions, and the purpose is to form a stable temperature environment and an atmosphere environment without oxygen and other impurity gases for the epitaxial step to ensure the formation of a high-quality polysilicon layer.

[0015] Step S11, introducing epitaxial gas into the surface of the single crystal silicon substrate to directly grow a polysilicon layer, the epitaxial gas is trichlorosilane, and the growth temperature is in the range of 850-950°C. Further, the flow rate of the directly grown polysilicon layer is 2-5 liters / minute. In this step, transition structures such as a seed layer or a seed crystal layer are not grown, but a polysilicon layer is directly grown. Studies have found that by using trichlorosilane and ensuring that the growth temperature is in the range of 850-950°C, such as 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, or 950°C, a polysilicon layer can be directly grown, eliminating the step of growing transition structures such as a seed crystal layer or a seed layer, thereby improving production efficiency and reducing process complexity and production costs. After selecting a temperature within the above range, the growth process has been growing under constant conditions. After setting the conditions in the process flow, the machine will adjust the output power control temperature according to the temperature feedback from the set infrared temperature probe, and the flow rate is controlled by the flow controller. Studies have found that reactions below this range cannot occur, and single crystal silicon grows at temperatures exceeding 975°C. The temperature between 975-950°C is a transition zone, and the reaction is difficult to control. 850-950°C is the optimal temperature. The gas flow rate can be adjusted experimentally based on data such as the structure of the reaction chamber, the position of the gas nozzle, and the size of the single crystal silicon substrate. And the thickness of the polysilicon layer and the lattice size of the polysilicon layer formed by the above method are controllable. The longer the growth time and the higher the growth temperature, the higher the thickness of the polysilicon. As the growth temperature increases in the range of 850-950°C, the size of the lattice also increases.

[0016] Attached Figure 2 The following is a scanning electron microscope photo of a product obtained by using an embodiment of the above process method. (a) is a transmission electron microscope photo of the surface of the polycrystalline layer, and (b) is a transmission electron microscope photo of the cross section of the polycrystalline layer. Specifically, the P-type single crystal silicon wafer is kept at 800°C in an epitaxial furnace, and the flow rate is controlled at 60 liters / minute under the condition of H2 atmosphere, and the holding time is 60 seconds. Then, the temperature is controlled within the range of 900°C, and the epitaxial gas trichlorosilane is introduced, the flow rate is controlled at 2.5 liters / minute, and the growth time is controlled at 200 seconds, so that a polycrystalline silicon layer with a thickness of about 2.3μm can be directly epitaxially grown on the single crystal silicon wafer. The growth rate of the surface polycrystalline silicon layer is controlled by controlling the flow rate of trichlorosilane and the length of the growth time, thereby controlling the thickness and quality of the polycrystalline silicon layer.

[0017] As another embodiment, a P-type single crystal silicon wafer is kept at 800°C in an epitaxial furnace, and the flow rate is controlled at 60 liters / minute under the condition of H2 atmosphere, and the holding time is 60 seconds. Then the temperature is controlled within the range of 800-950°C (according to a gradient temperature increase of 25°C), and the epitaxial gas trichlorosilane is introduced, the flow rate is controlled at 2.5 liters / minute, and the growth time is controlled at 200 seconds. The surface polycrystalline morphology difference is observed through an optical microscope. Figure 3 The following is a photo of the surface morphology at the above process temperature. After CMP processing, the surface roughness and morphology differences were observed by AFM. Figure 4 This is an AFM surface photo at the above process temperature. From the test, it can be seen that in the process of directly growing the polysilicon layer, as long as the temperature is controlled within the above range, its surface flatness meets the requirements.

[0018] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A polycrystalline silicon epitaxial growth method, characterized in that: The steps include: A substrate whose surface is a single crystal silicon material is placed in the epitaxial cavity; An epitaxial gas is introduced into the surface of the substrate to directly grow a polysilicon layer, the epitaxial gas is trichlorosilane, and the growth temperature is within the range of 850-950°C.

2. The method according to claim 1, characterized in that The substrate is kept in an epitaxial furnace at 800-900°C, H2 or N2 is introduced at a flow rate of 40-80 L / min, and the heat preservation time is 40-100 seconds.

3. The method according to claim 1, characterized in that The flow rate of the directly grown polysilicon layer is 2-5 L / min.

4. The method according to claim 1, characterized in that The substrate is a single crystal silicon substrate.

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